Method and system for irrigation

ABSTRACT

An electrically-driven separation apparatus can be utilized to desalinate seawater and/or brackish water to provide irrigation water having a desired sodium adsorption ratio (SAR).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Application Ser. No. 60/805,512, entitled “ELECTRODIALYSISFOR DESALINATION OF SEAWATER AND BRACKISH WATER FOR AGRICULTURAL USE”filed on Jun. 22, 2006, and to U.S. Provisional Application Ser. No.60/804,610, entitled “ELECTRODIALYSIS AND FILTRATION FOR AGRICULTURALWATER PRODUCTION,” filed on Jun. 13, 2006, both of which areincorporated herein by reference in their entirety.

BACKGROUND OF INVENTION

1. Field of the Invention

This invention relates to systems and methods of providing cropirrigation water as well as potable water and, more particularly, tosystems and methods of providing irrigation water and/or potable waterfrom water having unacceptable dissolved solids content.

2. Discussion of Related Art

Desalting or desalination refers to a water treatment process thatremoves salt from, for example, water. In some cases, the water sourceis brackish or seawater and desalting techniques thereof provides atleast a portion of municipal requirements for potable, drinking water.Desalination techniques typically include those based on distillation aswell as reverse osmosis techniques. The desalted water can also beconsumed in commercial and industrial applications as, for example,process feed water, boiler feed water, and irrigation water. Particularexamples of industries that may utilize desalted water include thepharmaceutical, mining, paper and pulp, and agricultural industries.

SUMMARY OF THE INVENTION

Some aspects of the invention provide one or more embodiments involvinga method comprising introducing water to be treated into anelectrically-driven separation apparatus to provide irrigation waterhaving a sodium adsorption ratio (SAR or RNa) value of less than about20. The SAR value can be determined according to the formula,

${SAR} = \frac{\lbrack{Na}\rbrack}{\sqrt{\lbrack{Ca}\rbrack + \lbrack{Mg}\rbrack}}$

where [Na] is the sodium species concentration, in mol/m³, in theirrigation water, [Ca] is the calcium species concentration, in mol/m³,in the irrigation water, and [Mg] is the magnesium speciesconcentration, in mol/m³, in the irrigation water.

Other aspects of the invention provide one or more embodiments involvingan irrigation system comprising an electrically-driven separationapparatus fluidly connected to a source of water to be treated and anirrigation water distribution system fluidly connected to theelectrically-driven separation apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, each identical or nearly identical component that isillustrated in various figures is represented by a like numeral. Forpurposes of clarity, not every component may be labeled in everydrawing.

In the drawings:

FIG. 1 is a schematic illustration of a system in accordance with one ormore features of the invention;

FIG. 2 is a schematic illustration of an irrigation system in accordancewith further features of the invention;

FIG. 3 is another schematic illustration showing yet another system inaccordance with still further features of the invention;

FIG. 4 is a graph showing representative ranges of acceptable levels ofwater characteristics in accordance with some aspects of the invention;

FIG. 5 is a graph showing the predicted sodium adsorption ratio ofdesalted water by electrodialysis relative to the total dissolved solidslevel utilizing monovalent selective cation membrane at various levelsof selectivity, in accordance with some features of the invention;

FIG. 6 is a graph showing staged treatment aspects of the invention toproduce treated water having one or more desirable characteristics;

FIG. 7 is a graph showing the influence of membrane selectivity on thetotal dissolved solids content of the product water treated in anapparatus in accordance with some embodiments f the invention; and

FIGS. 8A and 8B are graphs comparatively illustrating some of thecharacteristics of treated water produced by systems and techniques ofthe invention relative to other non-selective processes.

DETAILED DESCRIPTION

This invention is not limited in its application to the details ofconstruction and the arrangement of components set forth in thefollowing description or illustrated in the drawings. The invention iscapable of embodiments and of being practiced or of being carried out invarious ways beyond those exemplarily presented herein.

One or more aspects of the invention can involve systems and techniquesfor providing water suitable for agricultural facilities. Other aspectsof the invention can provide water potable water or water suitable forhuman use or consumption as well as for livestock and poultry. Somesystems and techniques of the invention can convert or otherwise rendernon-potable water suitable for agricultural, livestock, poultry, and/orhuman consumption. Still further aspects of the invention can involvesystems and techniques that preferentially or selectively remove somespecies over other species from a fluid to be treated to provide aproduct having one or more desirable characteristics. In contrast withnon-selective techniques, some selective removal aspects of theinvention can be more cost effective by avoiding or reducing additionalpost-treatment processes such as, blending. Thus, the systems andtechniques of the invention economically provide treated water that ismore suitable for an intended use.

In some embodiments of the invention, some types of species are retainedin the treated stream while other types of species are preferentiallyremoved. The resultant product fluid can be utilized in variousapplications and/or otherwise satisfy one or more objectives. Otheraspects of the invention can involve systems and techniques that providewater having one or more properties or characteristics tailored tosatisfy a particular purpose. Some embodiments of the invention can thusinvolve systems and techniques that provide one or more water streams orbodies that have one or more attributes that have been adjusted based onone or more parameters of the point of use or facility in which thestream or body is utilized.

Even further aspects of the invention can involve systems and techniquesthat economically provide water for agricultural, industrial,commercial, and residential service. Further, some particular aspects ofthe invention can involve providing water to serve a plurality ofrequirements or levels of purity or quality. Thus in some embodiments,the systems and techniques of the invention can provide one or morewater streams or bodies in a mixed use facility. Particularlyadvantageous aspects of the invention can involve providing theplurality of water streams or bodies, each of which may have differingwater quality levels, from a source of water having high solids content,to a plurality of points of use, each of which may have differingrequirements. Such aspects of the invention can provide systems andtechniques that treat, for example, non-potable water to render itpotable and/or suitable for irrigation, for livestock and/or poultryconsumption, and for human consumption or use.

In some aspects of the invention, water having a high level of one ormore objectionable species dissolved therein can be treated to remove orat least reduce the concentration of such species to an acceptablelevel. The one or more objectionable species can be any species thatrender the untreated water unsuitable for a particular application. Forexample, the water may contain a high level or undesirable concentrationof monovalent cations and/or anions which adversely or undesirablyhinders retention of water in soil or adsorption of or other species,including, for example, divalent or even multivalent species. If therequirement is pertinent to crop irrigation, the undesirable conditionor characteristic can involve water that contains one or more speciesthat affects the permeability and/or infiltration properties of the soilbeing irrigated. For example, some aspects of the invention can involverendering or treating water to preferentially remove monovalent speciesover non-monovalent species.

In accordance with one or more particular aspects, the invention caninvolve embodiments directed to systems and/or methods comprisingproviding or introducing water to be treated into an electrically-drivenseparation apparatus. Some embodiments of the invention can involve anirrigation system comprising an electrically-driven separation apparatusfluidly connected, or at least connectable, to one or more sources ofwater to be treated and at least one irrigation water distributionsystem.

In other aspects of the invention, some embodiments thereof can involvea method of providing potable water. Notably, some aspects of theinvention can provide irrigation water and/or potable water withoutthermally-driven separation techniques or unit operations. For example,in some embodiments of the invention, the method can comprise one ormore acts or steps of providing water to be treated and treating atleast a portion of the water to be treated in an electrically-drivenseparation apparatus to produce a first treated water. The method canfurther comprise one or more acts of treating a portion of the water tobe treated, typically a separate portion, in one or more pressure-drivenseparation apparatus to produce a second treated water. In some cases,the method can further comprise a step of mixing the first treated waterand the second treated water to produce the potable water. The potablewater typically has a target or desired total dissolved solids (TDS)content.

Aspects of the invention directed to systems that provide potable watercan comprise a source of water to be treated, a pressure-drivenseparation apparatus having an inlet that is fluidly connected, or atleast connectable, to the source of water to be treated. Thepressure-driven apparatus can also have one or more outlets, typicallyat least one product outlet as a treated water outlet. Thepressure-driven apparatus typically also has at least one reject outletas an outlet for a stream containing one or more species, typically theundesirable species, removed from the treated water. The system forproviding potable water can further comprise one or moreelectrically-driven separation apparatus which can be fluidly connected,or connectable, to the source of water to be treated, to thepressure-driven separation apparatus, or both. For example, as describedin further detail below, one or more electrically-driven separationapparatus can be fluidly connected to a reject outlet of thepressure-driven separation apparatus. In accordance with particularembodiments of the invention, the system for providing potable water canfurther comprise one or more mixers having one or more inlets fluidlyconnected, or connectable, to the treated water outlet of thepressure-driven apparatus and the product water outlet of theelectrically-driven separation apparatus. The mixer can comprise anymixing unit operation that facilitates at least partially blending orcombining one or more products streams including, in some cases, astream from the source of water to be treated to form a final productstream having one or more desirable characteristics.

The water to be treated can comprise seawater, brackish water, and/orwater containing high concentrations of dissolved solids or salts. Othersources of water to be treated can comprise water that would beunsuitable for use in agricultural facilities because of infiltrationand/or toxicity considerations.

The systems and techniques of the invention can comprise, whereappropriate, pre-treatment subsystems to facilitate one or moreoperating principles thereof. One or more pre-treatment andpost-treatment unit operations may be utilized in one or moreembodiments of the invention. For example, the systems and techniques ofthe invention may comprise a pre-treatment subsystem comprising one or aplurality of filters that separate or remove at least a portion of anysuspended solids in the water to be treated. Such pre-treatmentsubsystems typically remove particulate material that would damage anydownstream unit operation of the systems of the invention. Otherpre-treatment unit operations include, for example, microfilters as wellas sedimentary-based systems that can remove suspended solids that areone micron or greater.

Further pre-treatment operations may be utilized to improve theeffectiveness of one or more unit operations of the invention. Forexample, a pre-treatment subsystem can comprise cooler or heaters that,respectively, cool or heat the water to be treated prior to separationoperations. Cooling of the raw feed stream, or any intermediate processstream may be performed to, for example, facilitate the transport of anundesirable species, or to hinder the transport of a desirable species,from the stream to be treated. Likewise, heating may be performed toraise the temperature of the raw feed stream, or one or moreintermediate process streams, to a desired temperature that, forexample, facilitates economical or efficient operation of the one ormore separation apparatus. Non-limiting examples of heating processesmay involve heaters, furnaces, or heat exchangers that may be associatedor be a unit operation of a process or system of the invention. Forexample, heating may be provided through a heat exchanger of a powerplant that is not necessarily associated with the treatment systems ofthe invention.

Post-treatment unit operations may polish, remove, or reduce theconcentration one or more species in the treated water. For example, oneor more ion exchange columns may be utilized to remove species that arenot readily removed in the electrically-driven separation apparatusand/or the pressure-driven separation apparatus. Non-limiting examplesof species that would typically be removed or at least have a reductionin concentration to, preferably, non-toxic and/or non-objectionablelevels, in post-treatment operations include those that may affect soilaggregation, water infiltration, and/or would be toxic to plant growthsuch as aluminum, arsenic, beryllium, cadmium, cobalt, chromium, copper,iron, fluoride, lithium, manganese, molybdenum, nickel, lead, selenium,tin, titanium, tungsten, vanadium, boron, and zinc. Other species thatmay be addressed by one or more post-treatment operations include thosethat may be toxic or objectionable to humans, poultry, and/or livestockin drinking water such as, but not limited to, nitrates, nitrites, andvanadium, and sulfides. Disinfecting processes may also be performed toat least partially inactivate or reduce the concentration ofcolony-forming microorganisms that may be harmful to human and/orlivestock.

Alternatively, or in combination with the one or more polishing unitoperations, the systems and techniques of the invention may involveadding one or more species to at least a portion of the treated water.For example, gypsum may be added to adjust the concentration of one ormore desirable species or adjust a characteristic of the water. Otheradditives may include fertilizers or other supplements that facilitatecrop growth when the water is used for irrigation.

An electrically-driven apparatus typically utilizes a potential field tocreate a motive force that induces one or more species, typically thetarget species, which can include desirable as well as undesirablespecies, to migrate from the carrier or fluid. The electrically-drivenapparatus can utilize one or more components that segregate the targetspecies during migration and/or inhibit the return or reverse process.Non-limiting examples of such devices include electrodialysis (ED)devices, including current reversing electrodialysis (EDR) devices, aswell as electrodeionization (EDI) devices. The present invention,however, is not limited to one or a combination of suchelectrically-driven apparatus and may be practiced in other apparatusthat provide a motive force that facilitates the preferential migrationof one or more target species over other species in the fluid to betreated.

The electrically-driven separation apparatus of the invention typicallyutilize ion selective membranes to facilitate separation phenomena. Insome cases, the selectively permeable membrane can preferentially orselectively allow transport of some species relative to other species.For example, cation selective membranes may be utilized in somecompartments of the electrically-driven separation apparatus. In othercases, anion selective membranes may be utilized in one or morecompartments. In still other cases, the electrically-driven separationapparatus of the invention may comprise one or more monovalent selectivemembranes to selectively promote transfer of the monovalent cationic oranionic species. Indeed, in some embodiments of the invention, theseparation apparatus of the invention may comprise monovalent cationselective membranes and one or more monovalent anion selectivemembranes, typically in one or more concentrating compartments of theapparatus. Non-limiting examples of commercially available monovalentselective membranes include NEOSEPTA® cation and anion selectivemembranes from ASTOM Corporation, Tokyo, Japan or Tokuyama Corporation,Tokyo, Japan.

A pressure-driven separation apparatus typically utilizes one or morebarriers to inhibit migration therethrough while allowing penetration ofanother. The motive force facilitating the separation phenomenatypically involve pressurizing the fluid to be treated. Non-limitingexamples of pressure-driven separation apparatus includemicrofiltration, nanofiltration (NF) apparatus as well as reverseosmosis (RO) systems.

One or more embodiments of the invention can be directed to a watertreatment system 100 as exemplarily shown in FIG. 1. System 100 can be asystem for providing potable water, irrigation water, or both, to, forexample, a point of use 114. The treatment system 100 can comprise atleast one separation unit operation or separation apparatus 110 that, insome cases, selectively removes one or more species or types of speciesfrom the source 102 of water to be treated. The system can optionallycomprise one or more monitoring subsystems that provide an indication ofone or more operating characteristics of the treatment system. Asillustrated, system 100 can have one or more monitoring sensors 108 thattypically provide an indication of water quality produced, or otherwisetreated, from the separation apparatus 110. In some aspects of thepresent invention, system 100 can utilize a control system or controllerconfigured or constructed and arranged to regulate one or moreparameters of one or more unit operations in the systems of theinvention. Referring again to FIG. 1, system 100 can thus have one ormore controllers 106 that adjust at least one operating parameter ofseparation apparatus 110 typically to at least one desired condition.Any suitable control technique may be utilized to adjust the at leastone operating parameter of any unit operation in system 100 to providetreated water having the one or more desired characteristics.

The systems and techniques of the invention may include one or morewater distribution systems that facilitate delivery of the treated waterto one or more points of use. For example, the distribution system mayinclude an irrigation distribution system that delivers irrigation waterto various points of use in an agricultural facility. To facilitate thedelivery of the treated water, the distribution system can include oneor more storage systems, such as reservoirs, tanks, wells, or othervessels and containers. The irrigation systems of the invention mayutilize overhead and/or surface irrigation techniques to convey water toa designated area. The irrigation system components can thus employnon-movable as well as mobile devices.

The one or more storage systems that may be considered as part of thedistribution system or be an ancillary subsystem of the treatmentsystem. The one or more storage systems may further facilitate providingtreated water having desired characteristics. For example, treated waterhaving a first condition or characteristic may be stored in one or morestorage companions prior to further treatment or processing, e.g.,blending, with another treated or untreated water body or stream.

FIG. 2 is a schematic diagram exemplarily showing some features of theinvention pertinent to an irrigation system 200. Irrigation system 200can comprise a separation apparatus 230 fluidly connected and, asillustrated, disposed to receive water to be treated from source 202through irrigation water distribution system 224. Separation apparatus220 can treat water from source 202 and provide treated water to a firstpoint of use 228, illustrated herein as a first type of crop. Point ofuse 228 can be a portion of a crop that, for example, is at a stage ofgrowth different from at least one portion of the entire crop. System200 can further comprise one or more second separation apparatus 230.Separation apparatus 230 can also treat water from source 202 andprovide treated water to a second point of use 238, illustrated as asecond type of crop, through second irrigation distribution system 234.Point of use 228, second point of use 238 may be a portion the same typeof crop to be irrigated as, for example, first point of use 228 or aportion of a second crop at a different stage of growth. In accordancewith some embodiments of the invention, separation apparatus 230 canoptionally provide treated water to first point of use 228, instead ofand/or to supplement treated water from separation apparatus 220,through conduit or connection 244. Some embodiments of the inventioncontemplate, at least partially, a staged treatment scheme. For example,first separation apparatus 220 may provide treated water having a firstwater quality or characteristic which can further be treated in secondseparation apparatus 230 through conduit or distribution system 242. Aplurality of second separation apparatus 230 may be utilized with one ormore first separation apparatus 220 to provide treated water to one ormore points of use. Some embodiments of the invention may involve serialarrangement of separation apparatus and other embodiments may utilizeseparation apparatus in parallel configurations to provide treated waterso as to satisfy the volumetric requirements of the one or more pointsof use. In some cases, however, a combination of serial and paralleltreatment paths may be implemented to provide treated water at a rate ora plurality of rates, wherein each of the one or more treated waterstreams have one or more desired characteristics.

System 200 can include one or more controllers (not shown) to controlone or more operating parameters of any component or subsystem of system200. Like the system exemplarily illustrated in FIG. 1, system 200 canhave one or more controllers that can adjust one or more operatingparameters. For example, one or more controllers of system 200 can haveadjust the current, potential, or both, of the applied electric field inany of the separation apparatus. Other parameters that may be adjustedinclude, for example, TDS content, pressure, temperature, pH, flow ratioor any combination, of any stream of the system.

In accordance with some aspects of the invention, the one or morecharacteristics of the treated water stream can be any measured orderived attribute of the product stream so as to render it suitable forits intended use at point 114. However, the invention is not limited assuch; for example, the characteristic of the water may be an attributeof the treated or product water stream in terms relative to the waterstream to be treated. The attribute or parameter can be a singular or acomposite or aggregate characteristic of the water. Specific,non-limiting examples of such attributes can include the conductivity orresistivity of the water, the presence, absence, or concentration of onemore particular species or kinds of species in the water, as well ascombinations thereof.

In accordance with one or more embodiments of the invention, the systemsand techniques of the invention provide water having a desired waterattribute can be represented or quantified as a composite character. Thecomposite character can provide an indication of suitability of thetreated water for a particular purpose. Consequently, the systems andtechniques of the invention can involve operations that seek or at leastpromote providing water having one or more desired compositecharacteristics. In irrigation applications, the treated water attributecan be related to its suitability as irrigation water. Thus, someaspects of the invention can be directed to treating non-potable andrendering the water, as treated water, suitable for irrigation in one ormore agricultural facilities by adjusting one or more characteristicsthereof. Some aspects of the invention can provide irrigation watertailored one or more crops grown or cultivated in one or moreagricultural facilities. For example, with reference again to FIG. 2,the systems and techniques of the invention can provide a first treatedwater, having a first composite characteristic, to a first type of crop228 and a second treated water, having a second compositecharacteristic, to a second type of crop 238. The second treated watercan be used to supplement and/or adjust the characteristic of the firsttreated water and, conversely, the first treated water can be used toadjust one or more characteristics of the second treated water. The oneor more characteristics can be adjusted to meet a particular requirementby, for example, mixing together or blending the one or more treatedwater streams. The particular target characteristic can be achieved byregulating the ratios or relative amounts or rates of the treated waterstreams to be mixed.

During typical operation, each of the one or more separation apparatus220 and 230 typically generates one or more secondary streams.Typically, the one or more secondary streams contain an unacceptablelevel of one or more undesirable species. Any one or more secondarystreams can be discharged as waste streams. For example, the wastestream typically containing the one or more species transferred from thestream treated in separation apparatus 230, can be discharged ortransferred to the source of water to be treated 202 through conduit ordistribution system 236. Likewise, other embodiments of the inventioncontemplate combining one or more secondary streams, typically from oneor more downstream separation apparatus, with a water stream to betreated in one or more upstream separation apparatus. The waste streamcan also be discharged with other streams that may or may not bedirectly associated with the treatment system. For example, the streamto be discharged may be returned to the source of water to be treatedafter being mixed with one or more blow down streams from, for example,a cooling tower, which may not be a unit operation of the treatmentsystem. In other cases, however, the one or more waste streams may bestored and combined with water having very low salinity to mitigatewater infiltration problems that could result in leaching solubleminerals, and salts such as calcium from surface soils.

In some embodiments of the invention, the secondary stream contained inconduit 236 from second separation apparatus 230 can be introduced intofirst separation apparatus 220, alone or combined, as shown in FIG. 2,with water to be treated from source 202 as delivered through conduit222.

The schematically illustrated systems depicted in FIGS. 1 and 2 mayfurther comprise unit operations that facilitate the treatment of water.For example, an optional system may be utilized upstream of separationapparatus 220 and 230 to filter or otherwise remove at least a portionof suspended solids in the water from source 202. Non-limiting examplesof pre-treatment unit operations that may be utilized to reduce theconcentration of at least one suspended solid entrained in the water tobe treated include microfilters, settlers, and course particle filters.

Further, one or more unit operations may be utilized to further processone or more of the treated water streams. For example, a polishing bedmay further remove one or more species from one or more of the treatedstreams in distribution systems 224 and 234. Non-limiting examples ofsuch unit operations that can be utilized to remove at least a portionof weakly ionized or ionizable species, such as but not limited to,boron, selenite, and arsenic, include ion exchange columns.

Further unit operations that facilitate post-treatment of one or moretreated water streams of the invention include those that add orotherwise adjust a concentration of one or more desirable species orcharacteristics of the water stream. Post-treatment operations may beemployed to render the one or more waste streams suitable for dischargeto the environment.

Accordingly, a mixer may be disposed downstream of one or moreseparation apparatus of the invention that facilitates incorporation ofanother treated or untreated water stream, disinfectants, nutrients,and/or desirable salts from one or more sources of such. In accordancewith some embodiments of the invention, one or more sources of a saltcan be disposed to be introduced into the treated water stream. Forexample, a separation apparatus may be utilized in the treatment orirrigation system of the invention that selectively removes or reducesthe concentration of divalent or other non-monovalent species from awater stream to be treated. Such an optional apparatus would typicallyprovide at least product stream having a relatively high concentrationof non-monovalent species which can be introduced to the treated streamto adjust at least one characteristic thereof so as to provide a streamor body of water with a target or desirable condition. Examples ofsystems and techniques that advantageously provide beneficialspecies-rich streams include those disclosed in pending U.S. applicationSer. No. 11/474,299, titled “Electrically-Driven Separation Apparatus,”the substance of which is incorporated herein by reference. In somecases, however, one or more otherwise unconnected or distinct sourcesof, for example, calcium and/or magnesium salts, may be utilized toadjust one or more characteristics of the treated water stream prior toits use. Additionally, one or more intrinsic and/or extrinsic propertiesof the water stream may be further adjusted. For example, the waterstream may be cooled or heated to adjust the temperature thereof. The pHof the water stream or body may also be adjusted by, for example, addingone or more acids or bases, to achieve a desired pH value. The desiredproperty or characteristic may be dependent on a plurality of factorsincluding, for example, the pH of the soil to be irrigated, the salttolerance the crops to be irrigated and, in some cases, the moisturecontent of the soil. Thus, some features of the invention providefurther capabilities directed to achieving one or more desired compositecharacteristics.

The further adjustment of the one or more properties or characteristicsmay be performed after treatment in the separation apparatus, prior touse or introduction to the point of use, or during storage of thetreated water in one or more reservoirs.

However, some aspects of the invention contemplate beneficial oreconomically attractive attributes of such secondary streams containinghigh concentrations of one or more dissolved species, relative to thefirst or treated product stream and/or the stream introduced into theseparation apparatus. For example, the secondary product stream maycontain high dissolved solids and can serve as a feed stream that may befurther processed to obtain additional products or at least provide aproduct stream having a high concentration of a desirable species.

One or more characteristics of the water utilized in some systems andtechniques of the invention can provide an indication of the suitabilityof the water for agricultural use. For example, the one or morecharacteristics of the water can be represented as the salinity as totaldissolved salts or solids content, and/or electrical conductivity, aswell as or in conjunction with any of the alkalinity, iron content, andpH of the water. In some cases, the level of salinity of the water canbecome a selective parameter when considered relative to the type ofcrops to be irrigated by the at least partially treated water. Thus, inaccordance with some aspects of the invention, the salinity of the watermay be used to adjust at least one operating parameter of the systems ofthe invention. In other embodiments of the system and techniques of theinvention, the characteristic value can be represented as a ratio of theconcentration of species that tends to render soil as water-impermeablerelative to the concentration of species that tends to render soil asaggregating or water-adsorbing.

In accordance with some aspects of the invention, the characteristicvalue can provide an indication of the suitability of the water forirrigation purposes, for human consumption, and/or for livestock orpoultry use. In some embodiments, the characteristic value of a waterstream or body can be represented as a ratio of the concentration ofmonovalent species relative to the concentration of divalent species inthe water. For example, the characteristic value can be at leastpartially expressed as the sodium adsorption ratio or exchangeablesodium percentage. Preferably, the SAR value of a stream or body ofwater can provide an indication as to whether the water may be suitableto irrigate a type or kind of crop. Thus, in accordance with someaspects of the invention, some embodiments thereof relate to systems andtechniques that can involve controlling one or more operating parametersbased at least partially on a desired characteristic value that is atleast partially derived from at least one requirement of a point of use.Where the point of use is, for example, a crop to be irrigated, thedesired characteristic value can be based on the salt tolerance of thecrop and/or one or more attributes or characteristics of the soil.

The sodium adsorption ratio value is typically determined according tothe formula (1),

${SAR} = \frac{\lbrack{Na}\rbrack}{\sqrt{\lbrack{Ca}\rbrack + \lbrack{Mg}\rbrack}}$

where [Na] is the sodium species concentration, in mol/m³, in the water,[Ca] is the calcium species concentration, in mol/m³, in the water, and[Mg] is the magnesium species concentration, in mol/m³, in the water.Other characteristic values of the water may be utilized, alone or inconjunction with other characteristic values. Thus, in some cases, thecharacteristic value of the water that can serve as indication of waterquality or suitability for its intended purpose involves the totaldissolved solids concentration in the water, the pH, and/or theconcentration of one or more toxic or hazardous species.

Adjusting the SAR value of the, for example, irrigation water, may beeffected by adjusting one or more operating parameters of the watersystem. For example, the relative ratio of treated water having variousassociated SAR values may be adjusted to provide a composite or blendedmixture of product water having the desired SAR value. Other techniquesincluding reducing the flow rate of the water stream through the one ormore separation apparatus or increase the residence or treatment periodcan facilitate achieving the desired SAR value. In addition or inconjunction with such techniques, the applied potential level through,for example, the electrically-driven or pressure-driven separationapparatus can also provide treated water having the one or more desiredcharacteristics.

The treated water product of the systems of the invention may desalinateseawater and/or brackish water to provide irrigation water that avoidsor reduces the extent of any soil permeability and/or infiltrationproblems.

The one or more characteristic values of the treated water may be arelative correlation between species contained in the water. Forexample, the characteristic value may be a ratio of dissolved sodiumspecies to dissolved calcium. A preferred desirable sodium to calciumratio of not more than about 3:1 may avoid or reduce the likelihood ofwater infiltration problems due to soil dispersion and plugging and soilsurface pore sealing. Further, some embodiments of the invention canselectively reduce the concentration of monovalent sodium in irrigationwater, a source of relatively calcium-rich water can be provided tocounteract any sodium-dispersing phenomena in irrigation.

The product water can have an SAR value in a range from about 2 to about8. The target or desirable SAR value may, however, depend on one or morefactors in the agricultural facility. For example, the target SAR valuedepend on the type of crops grown in the facility, the stage of growthof one or more crops in the facility, and the soil conditions includingthe water infiltration, sodicity, and/or alkalinity of the soil.Particular guidelines that may be used to provide one or more targetcharacteristics of irrigating water include those provided by The Foodand Agriculture Organization of the United Nations (FAO). For example,the exchangeable sodium level, which can be correlated to the SAR value,can serve as a desirable characteristic value of water utilized forirrigation purposes. In particular, sensitive crops such as, but notlimited to fruits, nuts, and citrus typically require irrigation waterhaving an SAR value of up to about 8; other sensitive crops such asbeans may tolerate irrigation water having an SAR value of up to about18; moderately tolerant crops such as clover, oats, and rice maytolerate irrigation water having an SAR value of up to about 18 to 46;and tolerant crops such as, but not limited to wheat, barley, tomato,beets, and tall wheat grass, may tolerate irrigation water having an SARvalue of up to about 46 to 102.

Infiltration issues typically arise when irrigation water does not enterthe soil and becomes unavailable to crops. In contrast to salinityissues, which reduce the availability of water, infiltration problemscan effectively reduce the quantity of water available for crop use.Water infiltration can increase with increasing salinity and candecrease with decreasing salinity or increasing sodium content relativeto calcium and magnesium. Further, low salinity water, less than about0.5 dS/m, is typically corrosive and tends to leach surface soil ofsoluble minerals and salts, such as calcium, which in turn can reducesoil aggregation and structure. Soil without or having low salt contenttends to be dispersive, as fine soil particles, which fill pore spaces,effectively sealing the soil surface and reducing the rate of waterinfiltration. The soil would tend to form a crust which reduces theamount of water entering the subsurface and can also prevent cropemergence. Thus, in some embodiments of the invention, the desired waterquality may be further based on the salinity of the irrigation water.For example, FIG. 4, which is based on a publication by Ayers, R. S. andWestcot, D. W., titled “Water Quality for Agriculture,” FAO Irrigationand Drainage Paper 29 rev. 1, Food and Agriculture Organization of theUnited Nations, 1989, 1994, and which shows the influence of salinity,as represented by TDS concentration, and SAR on infiltration, canconjunctively provide desirable salinity levels and SAR values ofirrigation water that reduces or avoids infiltration problems. In FIG.4, seawater properties were used to derive TDS concentration values fromelectrical conductivity data from the above reference. In particular,the correlations between the density and salinity and between thesalinity and electrical conductivity of seawater at 20° C. weredetermined based on published physical properties. These correlationswere then used to convert the electrical conductivity values of seawaterfrom the above-identified reference into the corresponding TDSconcentration, which were then mapped relative to the corresponding SARvalues to obtain the infiltration guidelines presented in FIG. 4.

Further embodiments of the invention may also provide suitableirrigation water when it has a composite characteristic value such ashaving an SAR value of less than about 8 while having a TDS level ofabout 1,500 ppm or more.

Some embodiments of the invention can provide desalination systems andtechniques that selectively remove undesirable species which contraststo non-selective desalination techniques such as those based on thermaland pressure-driven processes. Further, some systems and techniques ofthe invention can provide product water stream without requiring thefurther addition of preferred species. For example, the invention canprovide irrigation water that does not involve further adjustingcharacteristic values by the addition of supplemental species.

FIG. 3 illustrates further features and aspects of the invention. Thetreatment system 300 exemplarily illustrated can comprise a firstseparation apparatus 304 and a second separation apparatus 306.Separation apparatus 304 and 306 typically treats a fluid from one ormore sources 302. The water to be treated from source 302 typicallycontains a high or unacceptable level of dissolved species. The one ormore separation apparatus can thus be utilized to at least partiallyremove or reduce the concentration of one or more undesirable speciesfrom the water. As exemplarily illustrated, treated water fromseparation apparatus 304 can be combined with treated water fromseparation apparatus 306 in one or more mixing operations or mixer 308to provide a treated water stream having desired properties and/orcharacteristics to point of use 314. In accordance with some embodimentsof the invention, the treated water may be rendered suitable to be usedas potable and/or bathing water in one or more points of use 314.

First separation apparatus 304 may be an electrically-driven apparatusor a pressure-driven apparatus. Likewise, second separation apparatus306 may be an electrically-driven separation apparatus or apressure-driven separation apparatus. In accordance with some aspects ofthe invention, separation apparatus 304 removes at least a portion of aplurality of undesirable species in water to be treated from source 302.In some cases, first separation apparatus can indiscriminately remove atleast a portion of a plurality of undesirable species from the water tobe treated. For example, the first separation apparatus can utilize ROand/or NF based techniques to remove, typically without preference orselectivity, at least a portion of any undesirable species. The treatedwater stream resulting from the pressure-driven separation apparatuspreferably exceeds potable water quality requirements.

The second separation apparatus can remove one or more undesirablespecies from the water stream to be treated. In some cases, theseparation apparatus selectively removes at least a portion one or moreundesirable species from the water to produce a product water stream. Ifthe product water stream from the second separation apparatus fails tomeet or exceed potable water quality requirements, a portion of thetreated water from the first separation apparatus that exceeds thepotable water quality requirements may be incorporated or blendedtherewith. For example, where the first separation apparatus providesproduct water having a TDS level of about 250 mg/L and the secondseparation apparatus provides product water having a TDS level of about1,000 mg/L, the product water streams can be combined in a volumetricratio of about 2:1 to produce a blended product having a TDS level ofabout 500 mg/L. The target level can be a concentration that meets orexceeds one or more guidelines suggested by the World HealthOrganization. Other water streams may also be blended with one or moreproducts streams of the separation apparatus of the invention to providedrinking and/or bathing water that meet or exceed guidelines orrequirements typically set by government regulatory organizations.

One or more reject streams from the first separation apparatus,typically containing relative high levels of species removed from thefirst treated product stream may be discharged to drain, directed to oneor more ancillary points of use 310, or returned to source 302. Furtherembodiments of the invention contemplate combining the reject waterstream with water from source 302 through conduit 322 so as to betreated in the second separation apparatus. A secondary or reject waterstream from second separation apparatus may also be discharged to adrain, directed to one or more ancillary points of use 310 and/or 312,returned to source 302, as shown through conduit 316.

As noted above, ancillary systems may be utilized in the systems andtechniques of the invention in post-treatment operations. For example,one or more disinfecting systems such as those that irradiate, oxidize,or otherwise reduce microbiological activity in the water may bedisposed to further treat the water. Further, one or more storagesystems as may be also used as discussed above.

Some features of the invention involve systems and techniques comprisingelectrically-driven separation apparatus utilizing selective membranesas discussed above. As illustrated in FIG. 7, the quality of the treatedwater as represented by for example, TDS content can be influenced bythe selectivity of the membrane utilized. FIGS. 8A and 8B show thecapabilities of the selective separation apparatus in accordance withsome aspects of the invention. As shown in FIG. 8A, water, having adesirable set of characteristics, can be produced for irrigating cropsby utilizing an electrically-driven separation apparatus. In someembodiments of the invention, electrically-driven separation apparatusutilize monovalent selective membranes to facilitate treating water,such as seawater and/or brackish water to provide water suitable forirrigation in agricultural facilities. In contrast, non-selectivetechniques or even non-monovalent selective techniques such as thosethat involve reverse osmosis apparatus, distillation apparatus as wellas nanofiltration, cannot flexibly provide treated water that meetstarget characteristics. FIG. 8B illustrates in particular thatelectrically-driven separation apparatus comprising monovalent selectivemembranes may provide treated water having acceptable sodium adsorptionratio character relative to TDS content above 2,500 or even 3,000 ppm.Thus, some aspects of the invention can provide systems and techniquesthat target removal of undesirable species while retaining lessobjectionable species.

Further, because some embodiments of the invention can selectivelyremove monovalent species, any resultant secondary or concentratestreams would be less susceptible to scaling and fouling. This featureadvantageously allows some separation embodiments of the invention tooperate at higher water recovery rates, compared to non-selectivetechniques, because the volumetric rate of any secondary streams can beeffectively reduced without or with less concern for undesirableprecipitation. Thus, some embodiments of the invention directed toutilizing systems and techniques that selectively separate monovalentspecies can be operated at higher recovery rates compared tonon-selective ED and distillation based separation apparatus, and evenmuch higher recovery rates compared RO and NF based separationapparatus. Significantly, because RO and NF based separation systemsselectively reduce the concentration of non-monovalent species, theseprocesses cannot effectively provide treated water having low SARvalues.

A further advantage of the selective separation systems and techniquesof the invention pertains to the reduction or removal of non-ionizedspecies that have little or no influence on crop growth. For example,silica is typically not preferentially removed in the ED-based systemsof the invention thereby avoiding any scaling or fouling concerns, insecondary streams, that typically arise when treating silica-containingwater in RO and distillation apparatus. In addition, because secondarystreams of some embodiments of the invention typically have reducedscaling tendencies, the recovery rates in the separation systems andtechniques of the invention are greater than the recovery rates of ROand distillation based systems.

Controller 106 of the systems of the invention may be implemented usingone or more computer systems. The computer system may be, for example, ageneral-purpose computer such as those based on an Intel PENTIUM®M-typeprocessor, a Motorola PowerPC® processor, a Sun UltraSPARC® processor, aHewlett-Packard PA-RISC® processor, or any other type of processor orcombinations thereof. The computer system may be implemented usingspecially-programmed, special-purpose hardware, for example, anapplication-specific integrated circuit (ASIC) or controllers intendedfor water treatment system.

The computer system can include one or more processors typicallyconnected to one or more memory devices, which can comprise, forexample, any one or more of a disk drive memory, a flash memory device,a RAM memory device, or other device for storing data. The memorycomponent or subsystem is typically used for storing programs and dataduring operation of the system 100 and/or the computer system. Forexample, the memory component may be used for storing historical datarelating to the parameters over a period of time, as well as operatingdata. Software, including programming code that implements embodimentsof the invention, can be stored on a computer readable and/or writeablenonvolatile recording medium, and then typically copied into the memorysubsystem wherein it can then be executed by one or more processors.Such programming code may be written in any of a plurality ofprogramming languages, for example, Java, Visual Basic, C, C#, or C++,Fortran, Pascal, Eiffel, Basic, or any of a variety of combinationsthereof.

Components of the computer system may be coupled by an interconnectionmechanism, which may include one or more busses that providecommunication between components that are integrated within a samedevice and/or a network that provide communication or interactionbetween components that reside on separate discrete devices. Theinterconnection mechanism typically enables communications, includingbut not limited to data and instructions to be exchanged betweencomponents of the system.

The computer system can also include one or more input devices, forexample, a keyboard, mouse, trackball, microphone, touch screen, and oneor more output devices, for example, a printing device, display screen,or speaker. In addition, computer system may contain one or moreinterfaces that can connect the computer system to a communicationnetwork, in addition or as an alternative to the network that may beformed by one or more of the components of the system.

According to one or more embodiments of the invention, the one or moreinput devices may include sensors for measuring parameters.Alternatively, the sensors, the metering valves and/or pumps, or all ofthese components may be connected to a communication network that isoperatively coupled to the computer system. For example, one or moresensors 108 may be configured as input devices that are directlyconnected to controller 106, metering valves, pumps, and/or componentsof apparatus 102 may be configured as output devices that are connectedto controller 108. Any one or more of such subcomponents or subsystemsmay be coupled to another computer system or component so as tocommunicate with the computer system over a communication network. Sucha configuration permits one sensor to be located at a significantdistance from another sensor or allow any sensor to be located at asignificant distance from any subsystem and/or the controller, whilestill providing data therebetween.

The controller can include one or more computer storage media such asreadable and/or writeable nonvolatile recording medium in which signalscan be stored that define a program to be executed by the one or moreprocessors. The medium may, for example, be a disk or flash memory. Intypical operation, the processor can cause data, such as code thatimplements one or more embodiments of the invention, to be read from thestorage medium into a memory that allows for faster access to theinformation by the one or more processors than does medium. The memoryis typically a volatile, random access memory such as a dynamic randomaccess memory (DRAM) or static memory (SRAM) or other suitable devicesthat facilitates information transfer to and from the one or moreprocessors.

Although the control system is described by way of example as one typeof computer system upon which various aspects of the invention may bepracticed, it should be appreciated that the invention is not limited tobeing implemented in software, or on the computer system as exemplarilyshown. Indeed, rather than implemented on, for example, a generalpurpose computer system, the controller, or components or subsectionsthereof, may alternatively be implemented as a dedicated system or as adedicated programmable logic controller (PLC) or in a distributedcontrol system. Further, it should be appreciated that one or morefeatures or aspects of the invention may be implemented in software,hardware or firmware, or any combination thereof. For example, one ormore segments of an algorithm executable by controller 106 can beperformed in separate computers, which in turn, can be communicationthrough one or more networks.

Although various embodiments exemplarily shown have been described asusing sensors, it should be appreciated that the invention is not solimited. The invention contemplates the modification of existingfacilities to retrofit one or more systems, subsystems, or componentsand implement the techniques of the invention. Thus, for example, anexisting facility, especially an agricultural or crop-growing facility,can be modified to include one or more systems configured to provideirrigation water, potable water, or both, accordance with any one ormore embodiments exemplarily discussed herein. Alternatively, existingsystems and/or components or subsystems thereof can be modified toperform any one or more acts of the invention.

EXAMPLES

The function and advantages of these and other embodiments of theinvention can be further understood from the examples below, whichillustrate the benefits and/or advantages of the one or more systems andtechniques of the invention but do not exemplify the full scope of theinvention.

Example 1

This example describes the expected performance of an ED apparatus whenutilized to selectively remove monovalent cations from a stream to betreated and produce treated water having a lower SAR value.

FIG. 5 is a graph showing the SAR value in the treated water utilizingvarious monovalent selective membranes, with differing levels ofselectivity. As shown, if the acceptable or desired SAR value is lessthan about 6, then a TDS level of about 3,500 ppm can be achieved with amonovalent selective membrane having a selectivity of about 5. Also, ifthe acceptable or desired SAR value is less than about 3, then a TDSlevel of about 2,700 ppm can be achieved with a monovalent selectivemembrane having a selectivity of about 10.

The predicted energy requirement for the ED apparatus is less than thepredicted requirement utilizing the RO apparatus. Further, the predictedenergy required to treat water in an electrically-driven separationapparatus of the invention is expected to be linearly affected by thesalinity of the water to be treated. In some embodiments of theinvention, the temperature of the feed stream can be adjusted to reducethe energy required to facilitate cost effective separation in anelectrically-driven separation apparatus. For example, increasing thetemperature of the feed stream comprising seawater by about 25° C. toprovide for a product TDS level of about 1,500 ppm and a recovery ofabout 50%, can result in a predicted energy reduction of about 6% in anED module.

Example 2

This example describes the performance of a system utilizing thetechniques of the invention as substantially represented in theschematic illustration of FIG. 1, except that a controller was notutilized to adjust an operating parameter of the system.

The ED stack was comprised of ten effective cell pairs of concentratingand diluting compartments, five cell pairs in a downward flow path andfive cell pairs in an upward flow path, providing for an overall fluidstream process flow path of about 28 inches. The cell pairs utilizedcation selective membranes, CMS monovalent selective homogeneousmembranes from Tokuyama Corporation to preferentially remove sodiumcations, and heterogeneous ion exchange membranes for the anionselective membrane (IONPURE™ anion membrane, 0.018 inches thick). Spacergaskets that were 0.020 inches thick and extruded screens about 70% openarea and 0.020 inches thick were used to at least partially define thecompartments. The ED apparatus was operated at an applied potential ofabout 2 volts per cell pair, through RuO₂-coated titanium electrodes.

The feed water was prepared by dissolving Instant Ocean® synthetic seasalt mixture, available from Spectrum Brands Inc., in deionized water.Sodium chloride was added as needed to provide a feed solution that hadan SAR value of seawater (about 54).

The module was operated in a once-through mode wherein both the diluteand concentrate streams were returned to the feed tank. The electrodechambers were constructed as dilute compartments and fed separately.Calcium and magnesium species concentrations in the feed and productstreams were determined by standard titration methods. The TDS level wascalculated based on the measured conductivity. The sodium concentrationwas also calculated.

Tables 1 and 2 respectively show the inlet and product water streamcharacteristics. As shown in Table 2, the systems and techniques of theinvention can provide a product water stream having one or more desiredcharacteristics. For example, the systems and techniques of theinvention can selectively reduce the concentration of monovalent speciesto provide water having a desired SAR value.

Further, the data presented in the tables show that coupling two or moreelectrically-driven separation apparatus can provide treated waterhaving a desired SAR value. That is, a first electrically-drivenseparation apparatus can lower the SAR value of a water stream toprovide an intermediate product stream having an intermediate SAR value.The intermediate product stream can in turn be introduced into a secondelectrically-driven separation apparatus to provide treated water havingthe desired SAR value. In particular, FIG. 6 shows that the TDS leveland SAR value can be reduced to desirable levels by utilizing EDapparatus, having monovalent selective membranes, in about three stagesbased on this configuration. Other configurations may involve more orless stages to achieve one or more desired water characteristics.

The data further shows that various parameter can be adjusted tailor theSAR value in the product water. For example, the processing flow ratecan be increased or decreased to achieve a target SAR value.Alternatively, or in conjunction with adjusting the flow rate, theapplied potential and/or overall flow path length can be used as anadjustable operating parameter in one or more aspects of the invention.

TABLE 1 Feed Stream Characteristics. Flow Rate Conductivity Ca Mg TDS NaSAR L/m mS/cm ppm ppm ppm ppm — 0.064 33.7 340 1940 24062 6397 29.40.072 33.7 340 1940 24062 6397 29.4 0.072 33.7 340 1940 24062 6397 29.40.076 34.7 352 1928 24836 6673 30.7 0.1 15.8 224 1196 10596 2418 14.10.122 33.7 340 1940 24062 6397 29.4 0.148 49.7 316 1784 37426 11339 54.4

TABLE 2 Product Stream Characteristics. Flow Rate Conductivity Ca Mg TDSNa SAR L/m mS/cm ppm ppm ppm ppm — 0.064 16.0 236 1584 10766 2094 10.70.072 16.2 252 1588 10880 2116 10.8 0.072 22.1 284 1756 15164 3453 16.80.076 24.8 292 1720 17159 4192 20.5 0.1 5.2 124 740 3374 374 2.8 0.12223.3 276 1724 16031 3800 18.6 0.148 36.4 268 1652 26163 7493 37.5

Example 3

This example compares the performance of electrically-driven separationapparatus to the performance of thermally-driven and pressure-drivenseparation apparatus.

The ED module utilized had ten cell pairs in a folded flow path so thatthe flow passed through five cell pairs of diluting and concentratingcompartments then turned and passed through another five cell pairs.Each cell in the module was comprised of a screen and a 0.020 inch thickspacer. The cells were 14 inches by 1.2 inches. The monovalent cationselective membrane utilized was a CMS membrane from Tokuyama SodaCorporation. The anion selective membrane utilized was an IONPURE™heterogeneous membrane. The ED module utilized platinum-coated titaniumplates. The applied voltages and current, flow rates and feedcompositions were varied to obtain various conditions of effectiveselectivity.

Tables 3 and 4 list the feed and product water stream properties. FIG. 7is a graph showing the influence of the TDS level of the treated waterrelative to the selectivity of the membrane utilized in the ED module.The TDS content of the feed and product streams as well as theconcentrations of sodium, calcium, and magnesium were analyzed. Thesemeasured values were utilized to calculate the effective selectivityaccording to the formula (2):

${Selectivity} = \frac{\frac{\Delta \; v_{Na}}{v_{Na}}}{2\lbrack \frac{{\Delta \; v_{Ca}} + {\Delta \; v_{Mg}}}{v_{Ca} + v_{Mg}} \rbrack}$

where ν is the molarity of ionic species i and Δν is the change in themolarity of ionic species i.

TABLE 3 Feed Stream Characteristics. Ca Mg TDS SAR Na ppm Ppm ppm — ppm1 126 428 37426 121.66 12822 2 141 1928 24836 75.42 8283 3 136 194024062 72.92 8009 4 136 1940 24062 72.92 8009 5 136 1940 24062 72.92 80096 136 1940 24062 72.92 8009 7 355 5112 40268 72.13 12850 8 306 439635028 67.75 11193 9 234 3396 27129 59.78 8674 10 163 2340 19281 51.296184 11 98 1336 11356 39.93 3651 12 90 1196 10596 39.45 3419 13 32 3844014 26.5 1313 14 32 384 4014 26.5 1313

TABLE 4 Product Stream Characteristics and Calculated Selectivity. Ca MgTDS SAR Na Selectivity ppm ppm ppm — ppm — 1 107 396 26163 87.84 88521.8 2 292 1720 17159 54.42 5614 1.4 3 276 1724 16031 50.72 5217 1.4 4252 1588 10880 34.66 3420 1.5 5 284 1756 15164 47.14 4897 1.8 6 236 158410766 34.51 3386 1.4 7 804 5036 34123 60.92 10707 3.1 8 704 4276 2934856.79 9217 2.5 9 536 3324 21566 47.05 6724 3.7 10 304 1972 8897 23.732604 1.7 11 188 1148 6187 22.26 1871 1.6 12 124 740 3374 14.58 986 0.913 44 236 1321 10.4 400 0.9 14 32 168 651 5.57 181 0.8

The data in Tables 3 and 4 as well as FIG. 7 show that as the TDScontent of the feed water decreases the selectivity of the cationselective membrane also decreases. The correlation of selectivity to TDSdetermined to follow the formula (3):

Selectivity=0.5905+(5×10⁻⁵)(TDS)

This selectivity/TDS relationship was then utilized to characterize thecapabilities electrically-driven separation apparatus in accordance withthe invention in terms of a composite characteristic as represented inFIGS. 8A and 8B, relative to other non-selective techniques reverseosmosis, distillation, and nanofiltration.

It is assumed that about 96% of the monovalent cationic species inseawater is sodium and about 4% is potassium. Further, all the cationicspecies is assumed to constitute about 37% of the TDS content such thatthe change in TDS can be determined according to the formula (4):

${{23( \frac{\Delta \; v_{Na}}{0.96} )} + {40( {\Delta \; v_{Ca}} )} + {24( {\Delta \; v_{Mg}} )}} = {0.37( {\Delta \; {TDS}} )}$

Further assuming that the divalent species calcium and magnesium behavesimilarly when being removed in the electrically-driven separationapparatus, the following formula can be utilized:

$\frac{\Delta \; v_{Ca}}{v_{Ca}} = {\frac{\Delta \; v_{Mg}}{v_{Mg}}.}$

The above assumptions utilizing formulas (2), (3), and (4) were used topredict the product water SAR value relative to TDS level. The resultsare presented in FIGS. 8A and 8B, the latter showing an enlarged sectionof the former. FIG. 8B, which includes an overlay defining a region ofpreferred characteristics for some crops, shows that the separationtechniques of the invention can provide a plurality of actual productstreams that satisfy or span the limits the set of targetcharacteristics. Notably, the separation systems and techniques of theinvention provide intermediate and/or tailorable features that cannot bedirectly achieved with the non-selective alternatives. Nonetheless, toprovide a comparative basis, intermediate properties of treated waterwere approximated by approximating an assumed blend of the actualresultant product with a proportionate amount of raw or untreatedseawater. For example, to provide an estimate of the nature of theSAR/TDS relationship for distilled water product, feed seawater wasmixed with actual distillate water to predict the characteristic valuesof an intermediate product. Although such practices are not typicalemployed, the illustrated predicted intermediate characteristics, asnoted by the dashed line connecting actual data, were presented toprovide a comparison relative to the selective separation systems. Thenature of the SAR/TDS relationship for reverse osmosis andnanofiltration systems were likewise approximated by estimating theproperties of a theoretically blended product. Thus, for each of thediscrete, non-tailorable technique, dashed lines connecting actual datapoints represent an hypothetically achievable tailorable product whereassolid lines connecting actual data values show achievable tailorableproduct.

The actual distillate water properties were obtained from a publicationby the U.S. Dept. of Interior, Bureau of Reclamation, Denver Office,titled “Water Treatment Technology Program Report,” no. 7, 1995. Theactual data for non-selective ED product water properties were obtainedfrom a publication by Turek, M., “Cost Effective ElectrodialyticSeawater Desalination,” Desalination, no. 153, pp. 371-376, 2002. Theactual data for nanofiltered product water properties were obtained froma publication by Tseng, et al., “Optimization of Dual-Staged NFMembranes for Seawater Desalination,” AWWA 2003 CA-NV An. Fall Conf.,2003.

Having now described some illustrative embodiments of the invention, itshould be apparent to those skilled in the art that the foregoing ismerely illustrative and not limiting. Numerous modifications and otherembodiments are within the scope of one of ordinary skill in the art andare contemplated as falling within the scope of the invention. Inparticular, although many of the examples presented herein involvespecific combinations of method acts or system elements, it should beunderstood that those acts and those elements may be combined in otherways to accomplish the same objectives. For example, ED and EDIapparatus may be combined in a two-stage process wherein the EDapparatus reduces the TDS level in seawater to a range of about 5,000ppm to about 6,000 ppm and the EDI apparatus subsequently reduces theTDS level to a range of about 1,500 ppm to about 2,000 ppm.

Further, acts, elements, and features discussed only in connection withone embodiment are not intended to be excluded from a similar role inother embodiments.

It is to be appreciated that various alterations, modifications, andimprovements can readily occur to those skilled in the art and that suchalterations, modifications, and improvements are intended to be part ofthe disclosure and within the spirit and scope of the invention. Forexample, the sodium adsorption ratio may be represented according to analternative formula (5):

${{adj}\mspace{14mu} {RNa}} = \frac{Na}{\sqrt{\frac{{Ca}_{x} + {Mg}}{2}}}$

where Na is the sodium concentration in the water, in me/L; Ca_(x) is amodified calcium value, in me/L, that represents calcium speciesconcentration in the water with compensation due to the salinity of thewater, the HCO₃/Ca ratio (in me/L), and the estimated partial pressureof CO₂ in the soil surface; and Mg is the concentration of magnesiumspecies in the water, in me/L.

Moreover, it should also be appreciated that the invention is directedto each feature, system, subsystem, or technique described herein andany combination of two or more features, systems, subsystems, ortechniques described herein and any combination of two or more features,systems, subsystems, and/or methods, if such features, systems,subsystems, and techniques are not mutually inconsistent, is consideredto be within the scope of the invention as embodied in the claims.

Use of ordinal terms such as “first,” “second,” “third,” and the like inthe claims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

Those skilled in the art should appreciate that the parameters andconfigurations described herein are exemplary and that actual parametersand/or configurations will depend on the specific application in whichthe systems and techniques of the invention are used. Those skilled inthe art should also recognize or be able to ascertain, using no morethan routine experimentation, equivalents to the specific embodiments ofthe invention. It is therefore to be understood that the embodimentsdescribed herein are presented by way of example only and that, withinthe scope of the appended claims and equivalents thereto; the inventionmay be practiced otherwise than as specifically described.

As used herein, the term “plurality” refers to two or more items orcomponents. The terms “comprising,” “including,” “carrying,” “having,”“containing,” and “involving,” whether in the written description or theclaims and the like, are open-ended terms, i.e., to mean “including butnot limited to.” Thus, the use of such terms is meant to encompass theitems listed thereafter, and equivalents thereof, as well as additionalitems. Only the transitional phrases “consisting of” and “consistingessentially of,” are closed or semi-closed transitional phrases,respectively, with respect to the claims. Further the use of the term“potable” with reference to water, especially treated water, does notlimit the scope of the inventive subject matter and can refer to watersuitable for livestock use, including consumption.

1. A method comprising introducing water to be treated into anelectrically-driven separation apparatus to provide irrigation waterhaving a sodium adsorption ratio (SAR) value of less than about 20,wherein the SAR value is determined according to the formula,${{SAR} = \frac{\lbrack{Na}\rbrack}{\sqrt{\lbrack{Ca}\rbrack + \lbrack{Mg}\rbrack}}},$where [Na] is the sodium species concentration, in mol/m³, in theirrigation water, [Ca] is the calcium species concentration, in mol/m³,in the irrigation water, and [Mg] is the magnesium speciesconcentration, in mol/m³, in the irrigation water.
 2. The method ofclaim 1, further comprising an act of heating the water to be treated.3. The method of claim 1, wherein the water to be treated comprises atleast one of seawater and brackish water.
 4. The method of claim 1,wherein the irrigation water has a total dissolved solids (TDS) contentof less than about 3,500 ppm.
 5. The method of claim 1, furthercomprising an act of adjusting a calcium species concentration of theirrigation water.
 6. The method of claim 1, further comprising an act ofadjusting a magnesium species concentration of the irrigation water. 7.The method of claim 1, further comprising an act of removing at least aportion of any boron-containing species in the irrigation water.
 8. Themethod of claim 1, wherein the electrically-driven separation apparatuscomprises a monovalent selective membrane.
 9. The method of claim 8,wherein the monovalent selective membrane is a monovalent cationselective membrane.
 10. The method of claim 8, wherein the monovalentselective membrane is a monovalent anion selective membrane.
 11. Themethod of claim 8, wherein the electrically-driven separation apparatuscomprises an electrodialysis device.
 12. The method of claim 1, whereinthe SAR value of the irrigation water is less than about
 9. 13. Themethod of claim 12, wherein the SAR value of the irrigation water isless than about
 3. 14. The method of claim 1, further comprising an actof removing suspended particulate material from the water to be treatedprior to performing the act of introducing the water into theelectrically-driven separation apparatus.
 15. The method of claim 14,further comprising an act of introducing the irrigation water into anion exchange bed.
 16. The method of claim 1, further comprising an actof irrigating at least a portion of an agricultural facility with theirrigation water.
 17. The method of claim 16, further comprising an actof adding at least one of seawater and brackish water to the irrigationwater to produce a blended irrigation water having a desired SAR value.18. The method of claim 16, further comprising an act of adjusting anoperating parameter of the electrically-driven separation apparatus toachieve a predetermined SAR value of the irrigation water based on atleast one requirement of the agricultural facility.
 19. The method ofclaim 18, wherein the at least one requirement is at least one of acharacteristic of soil in the agricultural facility and a salt toleranceof at least one crop growing in the agricultural facility.
 20. Anirrigation system comprising: an electrically-driven separationapparatus fluidly connected to a source of water to be treated; and anirrigation water distribution system fluidly connected to theelectrically-driven separation apparatus.
 21. The irrigation system ofclaim 20, wherein the electrically-driven separation apparatus comprisesan electrodialysis apparatus.
 22. The irrigation system of claim 20,further comprising a heater fluidly connected to the electrically-drivenseparation apparatus.
 23. The irrigation system of claim 20, wherein thewater to be treated comprises at least one of seawater and brackishwater.
 24. The irrigation system of claim 20, further comprising asource of at least one of magnesium salt and calcium salt, fluidlyconnected between the electrically-driven separation apparatus and theirrigation water distribution system.
 25. The irrigation system of claim20, further comprising a filter disposed upstream of theelectrically-driven separation apparatus.
 26. The irrigation system ofclaim 20, further comprising an ion exchange bed disposed upstream ofthe irrigation water distribution system.
 27. The irrigation system ofclaim 20, further comprising a controller configured to adjust at leastone operating parameter of the electrically-driven separation apparatus.28. The irrigation system of claim 27, wherein the controller isconfigured to adjust at least one operating parameter of theelectrically-driven separation apparatus to provide irrigation waterhaving a desired sodium adsorption ratio value.
 29. The irrigationsystem of claim 20, further comprising a mixer having an inlet fluidlyconnected to the electrically-driven separation apparatus and an outletfluidly connected to the irrigation water distribution system.
 30. Theirrigation system of claim 29, wherein the mixer further comprises aninlet fluidly connected to a source of water having a sodium adsorptionratio value of greater than about 20.